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SEAL WHISKERS DETECT WATER MOVEMENTS

SEAL WHISKERS DETECT WATER MOVEMENTS. Adapted from. Guido Dehnhardt, Bj örn Mauck and Horst Bleckmann. 1998. Seal Whiskers detect water movements. Nature. 394: 235-236. Soumya Ganguly Biol 657 April 21 2004. Habitat of Harbor Seals. Pinniped family.

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SEAL WHISKERS DETECT WATER MOVEMENTS

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  1. SEAL WHISKERS DETECT WATER MOVEMENTS Adapted from Guido Dehnhardt, Björn Mauck and Horst Bleckmann. 1998. Seal Whiskers detect water movements. Nature. 394: 235-236 Soumya Ganguly Biol 657 April 21 2004

  2. Habitat of Harbor Seals Pinniped family • Tend to haul out in areas which protects from land animals, has direct access to deep waters, proximity to food resource and protection from strong wind and waves. • Gregarious hauling out in small scattered groups. • Feed in conditions under which visibility is drastically reduced e.g. At night and in murky water.

  3. Orientation in the sea • Well nourished but blind seals can orient themselves successfully and hunt without vision. • Harbor seals and most other species belonging to the pinnipeds do not have an active sonar system • Water disturbances are the only probable kind of sensory information to be sensed in aquatic environment

  4. Whiskers:a hydrodynamic sensory tool • Whiskers are heavily innervated by slowly and rapidly adapting afferent fibers that respond to tiny deflection of hair shaft. • The pinnipeds including seals and sea lions use whiskers to discriminate touch and avoid obstacles. OBJECTIVE : To show that harbor seals use whiskers to detect low amplitude water movement to sense distance from other objects.

  5. The Technique : Go/no-go response paradigm • A stimuli was generated by an oscillating sphere attached to a long vibrator. • A trained seal was used which was blind folded and a headphone was placed to exclude the acoustic and optical signals. • Seal trained to place the head in a hoop opposite to the sphere where it pressed the tip of its lower jaw to a knob welded to the hoop. • Indication of water movement detection by the seal by leaving the hoop station. Dehnhardt et al. 1998 Effective stimulus amplitude calculated by knowing the exact distance between between the whiskers and the sphere.

  6. Results: • The blind folded seal brought its whiskers to the most forwarded position • No indication of active movement of protracted whiskers during the trial. • Responded to extremely weak hydrodynamic stimuli. • When muzzle or wire mesh was used to impede the whisker movement it never responded to the stimulus.

  7. Threshold curves • Particle displacement velocity and acceleration was plotted against the stimulus frequency. • Shows nearly constant acceleration value at a lower frequency range • The significant stimulus at a higher frequency range is the water displacement. • Threshold curves similar to that of the operation mode of the lateral line of fishes. Whiskers thus help seals to detect water velocity at speeds as low as 245 μm/s similar to the frequency range of “FISH GENERATED WATER MOVEMENT”.

  8. THANKS FOR YOUR ATTENTION

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